Embodiments of natural and synthetic lethal toxin neutralizing factors and their utility as treatment for envenomation

ABSTRACT

Opossum whole serum exhibits a life saving property by neutralizing the lethality of venoms from all major families of poisonous snakes, and therefore an injection of Opossum serum can used as a novel treatment for many types of envenomation. Preferably, the injectable treatment for envenomation should be a composition obtained from the fraction of Opossum whole serum which contains the lethal toxin neutralizing factor, i.e. the so called &#34;natural LTNF&#34;, in purity. A method is given for the manufacture of a lethal toxin neutralizing factor from the serum of an opossum (Didelphis virginiana) serum, by fractionating the opossum serum and isolating this select fraction from the plurality of fractions having an N terminal amino acid sequence given by SEQ ID No: 1. A short peptide was synthesized having SEQ ID No: 1. The synthetic peptide having sequence SEQ ID No: 1 shows lethal toxin neutralizing activity similar to the natural LTNF from opossum or mongoose sera. The synthetic LTNF also has life saving utility.

SPECIFICATION

This application is a continuation in part of the application Ser. No.08/058,387, filed May 10, 1993, now abandoned.

TECHNICAL FIELD

The present invention embodies a treatment for diverse envenomation andintoxication to be used in life saving applications. More particularly,the present invention relates to a molecular moiety called "lethal toxinneutralizing factor" for the treatment of venomous snake bites.

BACKGROUND OF THE INVENTION

Several warm-blooded animals, such as opossums, mongoose, meerkats, woodrats and cotton rats have shown a remarkable resistance to the toxicaction of snake venoms (1, 2 and 3). An antihemorrhagic factor in serumof Sigmodon hispidus (cotton rat), has been isolated and characterized(4). This antihemorrhagic factor has physical properties different fromthe immunoglobulins of serum. An antihemorrhagic factor has also beenisolated, purified and characterized from opossum serum (5, 6 and 7).The opossum serum derived antihemorrhagic factor has an isoelectric pH4.1 and molecular weight 68,000 daltons. According to the art of thepublished work, the antihemorrhagic factor in the serum of opossum isalbumin or closely associated with albumin. However, these investigatorsdid not claim the utility of antihemorragic factor as a treatment forsnakebite, nor did they measure its neutralizing activity versus venomtoxins except for observing its effect on skin hemorrhage.

This invention relates to: (1) the lethal toxin neutralizing effect ofopossum serum; (2) a purified component from opossum serum having lethaltoxin neutralizing activity; and (3) a synthetic peptide having similarlethal toxin neutralizing activity for crude venoms of various speciesof snakes containing diverse deadly toxins acting in differentphysiological ways. All three: opossum serum; the purified fraction fromopossum serum; and the synthetic peptide of the purified fractionprovide relatively universal treatment for snakebite. All threeneutralize venoms from the major families of poisonous snakes, andtherefore, provide a replacement for antivenoms made in horses.

Currently, antivenoms produced in horses provide the only availabletreatment for snakebite, in spite of the fact that some people arehypersensitive to horse proteins. Antivenom treatment for snakebite hasbeen in practice for over forty years without much improvement. The onlyconsideration being, that antivenoms for snake species prevalent to theregion be available, and that the correct antivenom should be used. Inorder to administer the proper specific antivenom, the victim orphysician must identify the guilty snake, which is impossible in manycases. Numerous antivenoms now exist worldwide, which are mostly made inhorse, although a few are made in goats. It would be desirable to findcombinations of venoms giving a broad spectrum of protective antibodies,but this has not yet happened.

Treatment of snakebite would be greatly enhanced, if a drug could befound which would overcome the problems associated with antivenoms. Adrug which will neutralize the toxicity of venoms from all major specieswill be a breakthrough.

REFERENCES CITED

U.S. Patent

1. U.S. Pat. No. 4/012,502 Mar. 15, 1977 Van B. Philpot, Jr.

OTHER PUBLICATIONS

0. Kilman J A, Toxicon 14:337-340 (1976).

1. Ovadia M and Kochava E, Toxicon 15:54 (1977).

2. Werner, R M and Vick J A, Toxicon 15:29 (1977).

3. Perez J, Haws W, Garcia V and Jennings B, Toxicon 16:375 (1979).

4. Pichyangkul S and Perez J C, Toxicon 19:205 (1981)

5. Menchaca J M and Perez J C, Toxicon 19:623 (1981).

6. ibid., pages 623-632.

7. Tomihara Yet al., Toxicon 25(6): 685-689 (1987).

8. Perales J, Toxicon 30 (5-6): 543 (1992). 9. Catanese J J and Kress LF, Biochemistry 31: 410-418 (1992)

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a compositionconsisting of a natural lethal toxin neutralizing factor (LTNF) derivedfrom opossum serum that serves as a relatively universal treatment forsnakebite. Said lethal toxin neutralizing factor being an effective lifesaving treatment for snakebite for a large variety of snakes havingdiverse type of lethal activities. It is a further object of the presentinvention to provide a lethal toxin neutralizing factor that does notinclude horse proteins.

It is also an object of the present invention to provide a shortsynthetic peptide which also has activity as a lethal toxin neutralizingfactor with the same or similar utility as the naturally occurringproduct. It is believed that the use of both natural and synthetic LTNFcan be extended to treat sepsis, allergy etc. and other nonspecificdisorders caused by environment.

Thus, both embodiments of the present invention, i.e. natural andsynthetic LTNF, can become alternative treatments for various snakebitesrequiring extremely low concentrations of protein; and it is believedthat their use can be extended to treat scorpion and bee stings, andalso toxins from plats, bacteria, etc. It is further believed that thisinvention has military applications due to the variety of unknownexposures that can occur under military conditions.

Both natural and synthetic LTNF should be given intravenously in amanner similar to an antivenom treatment to give a systemic effectrather than given topically or by perfusing the bite-wound to give alocalized effect such as antihemorrhage.

BRIEF DESCRIPTION OF THE DRAWINGS

Drawing 1 shows the high pressure liquid chromatography profile ofopossum serum using an anion exchange column. Peak number six representsthe lethal toxin neutralizing factor, LTNF.

Drawing 2 shows the high pressure liquid chromatography profile of aconcentrate from fraction number six showing a single peak of purenatural LTNF.

Drawing 3 shows the electrophoretic profile of opossum serum andpurified natural LTNF on a 14% Novex gel with markers. The molecularweight of natural LTNF corresponds to the albumin component of theopossum serum and the marker bovine serum albumin, which isapproximately 68,000 daltons.

SUMMARY OF THE INVENTION

The present invention is a method of producing a naturally occurring anda synthetic lethal toxin neutralizing factor having utility as a lifesaving agent for use with diverse venoms and toxins. The naturallyoccurring factor requires: (1) obtaining opossum serum; (2)fractionating the opossum serum into a plurality of fractions; (3)identifying and isolating the fraction having the lethal toxinneutralizing activity for venoms from the major families of poisonoussnakes. The synthetic factor requires: (1) Amino acid sequencing of thepurified LTNF from opossum serum; and (2) synthesizing a short peptideof fifteen amino acids, which is identical to the first 15 N terminalamino acids of the naturally occurring factor from opossum serum. Thesynthetic lethal toxin neutralizing factor and the first 15 N-terminalamino acids of the naturally occurring factor have the sequence:

Leu-Lys-Ala-Met-Asp-Pro-Thr-Pro-Pro-Leu-Trp-Ile-Lys-Thr-Glu, which willbe referred to as SEQ ID No:1.

The purification of the naturally occurring lethal toxin neutralizingfactor includes fractionating the opossum serum on an anion exchangecolumn of a liquid phase fractionating system. This liquid phasefractionating system is a high pressure liquid chromatography system.The fractions of the opossum serum are eluted with a buffer material.This buffer material is an aqueous gradient Trizma-HCl buffer having thepH 7.4 and molarity in the gradient range of 0.01 molar to 1.0 molar.

The eluted fractions of opossum serum are dialyzed against distilledwater as to remove the buffer chemicals. Initially, all fractions weretested for the lethal toxin neutralizing activity and the one fractionhaving such activity is called the lethal toxin neutralizing factor,"LTNF". This is a reproducible procedure and the same fraction alwayshas the lethal toxin neutralizing activity for various venoms.

Lethality of venom can be due to several types of toxins present in thevenom which exert different physiological effects, such as respiratoryfailure, blood clotting, muscular paralysis, cardiac arrest, cell lysisand hemorrhage; whereas, hemorrhage is only one of many causes of deathdue to envenomation. The lethal toxin neutralizing factor exhibits theability to neutralize all effects associated with the lethality of snakevenom toxins in mice. The lethal toxin neutralizing factor of thepresent invention shows inhibition or neutralization of toxins from thevenoms of major families of snakes. The molecular weight of the opossumderived lethal toxin neutralizing factor is about 68 kDa. The sequenceof the first fifteen amino acids from the N terminal is SEQ ID No: 1.

The synthesized peptide having the first fifteen amino acid sequencefrom the N terminal shows similar neutralization activity for toxinsfrom venoms when tested in mice. An extremely low concentration of thislethal toxin neutralizing factor is required to neutralize the lethaleffect of snake venoms in comparison to the protein concentrationrequired using currently available antivenom. Thus, both compositions ofthe present invention natural and synthetic LTNF can become alternativetreatments for various snakebites and it is believed that their use canbe extended to treat scorpion and bee stings, including toxins fromplants, bacteria, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Drawing 1 shows the high pressure liquid chromtography profile ofopossum serum using an anion exchange column. Peak number six representsthe toxin neuralizing factor, LTNF.

Drawing 2 shows the high pressure liquid chromatography profile of aconcentrate from fraction number six showing a simgle peak of purenatural LTNF.

Drawing 3 shows the electrophoretic profile of opossum serum andpurifiled natural LTNF ona 14% Novex gel with markers. The molecularweight of nature LTNF corresponds to the albumin cmponent of the opossumand the marker bovine serum albumin, which is approximately 68,00daltons.

DETAILED DESCRIPTION OF THE INVENTION

Whole sera from opossum and mongoose were tested for their neutralizingproperty versus several snake venoms belonging to four major families ofpoisonous snakes: Crotalidae, Elapidae Hydrolidae and Viperidae. Thefollowing sample of venoms were tested:

    ______________________________________                                        Crotalus adamanteus,                                                                              Family Crotalidae                                         Crotalus atrox      Family Crotalidae                                         Naja n. atra        Family Elapidae                                           Naja n. kaouthia    Family Elapidae                                           Vipera russellii    Family Viperidae                                          Oxyuranus scutellatus                                                                             Family Elapidae                                           Sea Snake           Family Hydrolidae                                         ______________________________________                                    

In order to measure the inhibition of toxicity, mice were injected witha predetermined lethal dose of the respective venoms in 0.1 ml volumeintraperitoneally. Immediately, the control mice were injected with 0.5ml 0.05M phosphate buffer saline (PBS) and the experimental with samevolume of opossum or mongoose serum. For each experimental category,three (3) mice were used.

                  TABLE I                                                         ______________________________________                                        NEUTRALIZATION OF LETHAL EFFECTS                                              OF SNAKE VENOMS BY                                                            OPOSSUM SERUM IN MICE                                                                          Death/Survival                                               Venom            Opossum Serum                                                                             Control                                          ______________________________________                                        Crotalus adamanteus                                                                            0/3         3/0                                              Crotalus atrox   0/3         3/0                                              Naja n. atra     0/3         3/0                                              Naja n. kaouthia 0/3         3/0                                              Vipera russellii 0/3         3/0                                              Oxyuranus s. scutellatus                                                                       0/3         3/0                                              Sea Snake        0/3         3/0                                              ______________________________________                                    

The results of Table I clearly show that opossum serum is renderingprotection against lethal doses of various snake venoms from allfamilies of poisonous snakes. The mice in controls died within 24 hours.As little as 0.5 ml of opossum serum is adequate to cause neutralizationand render protection from the envenomation which otherwise would belethal.

Opossum and mongoose sera were fractionated into immunoglobulin andalbumin components by saturated ammonium sulfate treatment. Theprecipitated immunoglobulin component was dissolved in 0.05M PBS to thestarting volume of the serum. After dialysis, both albumin andimmunoglobulin components were tested versus lethal doses of varioussnake venoms. The mice were injected with predetermined lethal doses ofsnake venoms followed by inoculation with 0.5 ml of albumin orimmunoglobulin components. The results are presented in table II.

                  TABLE II                                                        ______________________________________                                        NEUTRALIZATION OF LETHAL EFFECTS                                              OF SNAKE VENOMS IN MICE                                                       BY OPOSSUM SERUM ALBUMIN COMPONENT                                                          Death/Survival                                                                Albumin   Immnoglobulin                                         Venom         Component component                                             ______________________________________                                        C. atrox      0/3       3/0                                                   N. n. kaouthia                                                                              0/3       3/0                                                   V. russellii  0/3       3/0                                                   ______________________________________                                    

The results of the Table II clearly show that the protective factorresides in the albumin component of the opossum serum for the venoms ofC. atrox, N.n. kaouthia and V. russellii. Thus, the neutralization ofthe toxic effects of venoms is not due to antigen antibody reaction.

Opossum serum was fractionated on a liquid phase fractionating system.Specifically, using a high pressure liquid chromatography (HPLC), fromToso Co. Japan and anion exchange column (Type PL-SAX Q 1125, with 10μparticles, 1000 Å pores and column dimensions 150×10 mm) from PolymerLaboratories UK, maintained at 20° C. temperature. Approximately 25 mgof serum protein was loaded into the column to fractionate. The elutionwas accomplished with gradient Trizma-HCl buffer having pH 7.4 andmolarity gradient in the range 0.01M to 1.0M. Nine different fractionswere obtained which were individually pooled from several HPLC runs(Drawing no. 1). All fractions were dialyzed and concentrated usingSpectrum dialysis apparatus. The protein concentration for each fractionwas measured on spectrophotometer using protein assay kit from Bio-Radcompany. Each fraction was adjusted to 1 mg/ml concentration of theprotein content. Each fraction was mixed with an equal volume lethaldose of venom from C. atrox. In this case, 100 μg of the protein fromeach fraction was tested versus a predetermined lethal dose of C. atroxvenom.

                  TABLE III                                                       ______________________________________                                        IDENTIFICATION OF VENOM NEUTRALIZING                                          FACTOR FROM OPOSSUM SERUM                                                     Fraction #   Death/Survival                                                   ______________________________________                                        1            3/0                                                              2            3/0                                                              3            3/0                                                              4            3/0                                                              5            3/0                                                              6            0/3                                                              7            3/0                                                              8            3/0                                                              9            3/0                                                              ______________________________________                                    

The results of Table III show that the lethal toxin neutralizing factorresides in fraction number 6 of the nine different fractions for C.atrox venom.

One hundred micrograms of purified fraction no. 6, which is the lethaltoxin neutralizing factor, natural LTNF, was mixed with an equal volumeof the predetermined lethal doses of snake venoms to inject mice. Theresults are presented in table IV.

                  TABLE IV                                                        ______________________________________                                        NEUTRALIZATION EFFECT OF                                                      FRACTION 6 OF OPOSSUM SERUM                                                                   Death/Survival                                                Venoms          Fraction 6                                                                              Control                                             ______________________________________                                        C. atrox        0/3       3/0                                                 Vipera russellii                                                                              0/3       3/0                                                 N. n. kaouthia  0/3       3/0                                                 O. s. scutellatus                                                                             0/3       3/0                                                 Sea Snake       0/3       3/0                                                 ______________________________________                                    

The fraction 6 is the natural LTNF showing ability to neutralize thetoxic lethal effects of venoms of snakes from the major families. Thefraction number six was concentrated and rerun on the HPLC underidentical conditions of temperature, gradient buffer, etc. and ityielded one peak (Drawing no. 2). The material from this single peak waspartially sequenced for its first fifteen amino acids of the N-terminal.Furthermore, a peptide for those fifteen amino acids was synthesized.The sequenced amino acids of N-terminal were identified as SEQ ID No: 1.The molecular weight of natural LTNF was determined by gelelectrophoresis. The molecular weight of natural LTNF was reveled to beapproximately 68,000 daltons corresponding to the albumin component ofthe opossum serum. The molecular weight of the synthetic LTNF is lessthan 6,000 daltons (Drawing no. 3).

The synthesized LTNF was tested with the venoms as documented in TableV. Mice were divided into three groups. Mice in groups I & II wereinjected with lethal doses of respective venoms. Immediately, the micein group I were injected with 0.5 ml of PBS, while those in group IIwere injected with 500 μg of synthetic LTNF in 0.5 ml. Mice in group IIIwere injected with 500 μg of synthetic LTNF and after 30 minutes theywere given lethal doses of respective venoms. The results are presentedin table V.

                  TABLE V                                                         ______________________________________                                        NEUTRALIZATION EFFECT OF SYNTHETIC LTNF                                                  Death/Survival                                                                Group I    Group II   Group III                                               (PBS       (LTNF      (LTNF  1/2                                   Venoms     Control)   Immediately)                                                                             hr before)                                   ______________________________________                                        C. atrox   3/0        0/3        0/3                                          N. n. kaouthia                                                                           3/0        0/3        0/3                                          V. russellil                                                                             3/0        0/3        0/3                                          O. scutellatus                                                                           3/0        0/3        0/3                                          Sea Snake  3/0        0/3        0/3                                          ______________________________________                                    

The results of Table V clearly show the strong antilethal activity ofsynthetic LTNF, similar to the natural LTNF, which is identified inopossum serum. The lack of antigenic relationship between snake venomand opossum serum or LTNF, indicates that its activity is immunoglobulinindependent. Therefore, the activity of synthetic LTNF, which is similarto the natural LTNF, may extend to other toxins, viruses, allergens,etc. The antilethal activity of synthetic LTNF was exhibited when it wasadministered 1/2 hour before the toxin injection, therefore, syntheticLTNF can be used as a preventive measure, especially for snake handlers,etc.

As was described previously, the opossum whole serum exhibits theproperty of neutralizing the lethality of venoms from major families ofpoisonous snakes. Because the neutralizing activity of opossum serumresides in the albumin component of the opossum serum, this neutralizingactivity is not due to the antigen antibody reaction.

In the present invention, opossum serum was fractionated by highpressure liquid chromatography using an a anion exchange column. Theprocedure yielded nine different fractions. The lethal neutralizingfactor was found in fraction number six (Drawing no. 1). This fractionshowed the neutralization of snake venoms. Fraction 6 was concentratedand fractionated a second time on HPLC under identical conditions. Thepurified product gave a single peak in the HPLC profile (Drawing no. 2).The molecular weight of the purified material was 68 kDa as revealed bygel electrophoresis (Drawing no. 3).

One hundred micrograms of natural LTNF neutralized the lethal toxicityof a variety of venoms. The natural LTNF exhibits the sequence for itsfirst fifteen amino acids as SEQ ID No: 1. The known sequence of thefifteen amino acids of natural LTNF was synthesized as a short peptide.Five hundred micrograms of the synthetic LTNF is capable of neutralizinglethal doses of venoms from snakes from major families. Moreover, thesynthetic LTNF is immunogenic, since mice immunized with it were able toproduce specific antibodies, which reacted with both natural andsynthetic LTNF, thus proving its biological potency. The use of naturaland synthetic LTNF can be expected to treat sepsis, allergies and othernonspecific disorders caused by the environment and as a preventivemeasure before possible exposure to various toxins.

The natural LTNF can be isolated from other species of opossums such asDidelphis marsupialis, Philander opossum, and Lutreolina crassicaudataand other animals like mongoose and meerkat.

The application of natural or synthetic LTNF, as treatment forsnakebite, overcomes the problem of hypersensitivity occurring from thehorse-derived antivenom.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof. Various changes in the steps ofthe described method, or the details of the claim composition, can bemade within the scope of the appended claims without departing from thetrue spirit of the invention.

    __________________________________________________________________________    SEQUENCE LISTING                                                              (1) GENERAL INFORMATION:                                                      (iii) NUMBER OF SEQUENCES: 1                                                  (2) INFORMATION FOR SEQ ID NO: 1:                                             (i) SEQUENCE CHARACTERISTICS:                                                 (A) LENGTH: 15                                                                (B) TYPE: AMINO ACID                                                          (C) STRANDEDNESS: SINGLE                                                      (D) TOPOLOGY: LINEAR                                                          (ii) MOLECULE TYPE: PROTEIN IN SEQ ID NO: 1                                   (iii) HYPOTHETICAL: NO                                                        (iv) ANTI-SENSE: NO                                                           (v) FRAGMENT TYPE: N                                                          (vi) ORIGINAL SOURCE: OPOSSUM SERA: SEQ ID NO: 1:                             (A) ORGANISM: DIDELPHIS VIRINIANA                                             (B) STRAIN: WILD                                                              (C) INDIVIDUAL ISOLATE: TEXAS WILD                                            (D) DEVELOPMENTAL STAGE: ADULT                                                (E) HAPLOTYPE:                                                                (F) TISSUE TYPE: BLOOD                                                        (G) CELL TYPE:                                                                (H) CELL LINE:                                                                (I) ORGANELLE:                                                                (vii) IMMEDIATE SOURCE: OPOSSUM SERA SEQ ID NO: 1:                            (A) LIBRARY:                                                                  (B) CLONE:                                                                    (x) PUBLICATION INFORMATION:                                                  (A) AUTHORS: JONAS PERALES, ET AL.                                            (B) TITLE: ANTI-SNAKE VENOM FORM DIDELPHIDAE                                  (C) JOURNAL: INTERNATIONAL SOCIETY ON                                         TOXINOLOGY                                                                    (D) VOLUME: 10TH WORLD CONGRESS ON ANIMAL                                     PLANT AND MICROBIAL TOXINS 3-8 NOV 1991,                                      SINGAPORE                                                                     (E) ISSUE: PROGRAMME AND ABSTRACTS                                            (F) PAGES: 104                                                                (G) DATE: 3-8 NOV 1991                                                        (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 1:                                      LeuLysAlaMetAspProThrProProLeu                                                510                                                                           TrpIleLysThrGlu                                                               15                                                                            __________________________________________________________________________

We claim:
 1. A method for treating a victim of envenomation, said methodcomprising injecting intravenously a composition into said victim,wherein said composition contains a lethal toxin neutralizing factorobtained from the sera of an opossum from the family Didelphis, whereinthe victim has been envenomated by a bee.
 2. A method for treating avictim of envenomation, said method comprising injecting intravenously acomposition into said victim, wherein said composition contains a lethaltoxin neutralizing factor obtained from the sera of an opossum from thefamily Didelphis, wherein the victim has been envenomated by a scorpion.3. A method for treating a victim of a bacterial toxin said methodcomprisinginjecting intravenously a composition into said victim;wherein said composition comprises a lethal toxin neutralizing factorobtained from an animal having resistance to envenomation.
 4. A methodas in claim 3 wherein the animal is selected from the group consistingof Didelphis marsupialis, Philander opossum, and Lutreolinacrassicaudata and the factor has a molecular weight of approximately68,000 Daltons, and the first 15 amino acids from the N-terminus areidentified in SEQ ID NO:
 1. 5. A method for treating a victim of a planttoxin said method comprising injecting intravenously a composition intosaid victim; wherein said composition compromises a lethal toxinneutralizing factor obtained from an animal having resistance toenvenomation.
 6. A method as in claim 5 wherein the animal is selectedfrom the group consisting of Didelphis marsupialis, Philander opossum,and Lutreolina crassicaudata and the factor has a molecular weight ofapproximately 68,000 Daltons, and the first 15 amino acids from theN-terminus are identified in SEQ ID NO:
 1. 7. A method for treating avictim of envenomation, said method comprising injecting intravenouslyinto said victim a lethal toxin neutralizing factor comprising a 15amino acid peptide having a sequence given by SEQ ID NO: 1, wherein thevictim is envenomated by a bee sting.
 8. A method for treating a victimof envenomation, said method comprising injecting intravenously intosaid victim a lethal toxin neutralizing factor comprising a 15 aminoacid peptide having a sequence given by SEQ ID NO: 1, wherein the victimis envenomated by a scorpion.
 9. A method for treating a victim of a beesting said method comprising applying topically to said victim asolution containing a lethal toxin neutralizing factor comprising a 15amino acid peptide having a sequence given by SEQ ID NO: 1 at an areaaffected by the bee sting.
 10. A method for treating a victim of a planttoxin said method comprising injecting intravenously into said victim alethal toxin neutralizing factor comprising a 15 amino acid peptidehaving a sequence given by SEQ ID NO:
 1. 11. A method for treating avictim of a bacterial toxin said method comprising injectingintravenously into said victim a solution containing a lethal toxinneutralizing factor comprising a 15 amino acid peptide having a sequencegiven by SEQ ID NO: 1.